Production of primary and secondary amines



= Patented Oct. 30,. 1945 UNITED STATES PATENT OFFICE I Q I asaaosi a PRODUCTION OF PRIMARY AND SEOONDARYAMINES Barnard S.Biggs', Summit, N. 1, assignor to Bell Telephone Laboratories, Incorporated, New

York, N. Y., a corporation of New York Application August 14, 1941,'Serlal No. 406,835

t 4Cialms. (Cl.26i)583) This invention relates to new methods oi forming secondary amines or more particularly mixtures 01' primary and secondary amines. The

methods of this invention are particularly suited to the preparation of mixtures of primary and secondary diamines.

The method commonly used for the production drogenation'oi the corresponding dinitriles. This reaction is ordinarily carried out in the presence oi" a relatively high concentration of ammonia in order to suppress und'esirable'side reactions. In the absence oi. ammonia, the yield of diamines is low due to the formation of p'olyamines containing more than two amino groups and other undesired products. Typical or a common comer-- of primary diamines consists of the catalytic hyconditions of operation. The substituent on the I secondary amino group'is the radicalattached to the amino group of the primary monoamine.

The course of the reaction invcivedin the process or the present invention as applied, for instance, to the production or hexamethylene-diamine containing both primary and secondary amino groups, the secondary group having -a methyl substituent, is illustrated by the following qualitative equation:

.cial, process for producing diamines in this manher is the hydrogenation of adiponitrile to form hexamethylene diamine asi'ollows:

by a variation .in the ratio of primary to sec-- ondary amino groups in the diamines.

The methylamine or other primary monoamine acts tosuppress the undesired side reactions in much the same manner as does ammonia. when the monoamine is present in suiliciently high concentration, considerably in excess of the theoretical amount required for reaction, extremely high yields oi diamines are obtained. If. on the other hand, the dinitrile is hydrogenated in the absence or any suppressor, such as a primary monoamine or ammonia, the yield of diamines is ordinarily no more than about 50 per cent, the

remainder being lost as undesired 'polyamines and other products.

According to the present invention, a process is provided which will furnish simply and economically a source of diamines containing both primary and secondary amino groups in an easily varied ratio. 1 The process of the present invention resides in the catalytic hydrogenation of a dinitriie in the presence of a primary monoamine and ammonia.

. The product is a mixture containing a .diprimary amine, a primary-secondary amine and a discoondary amine. These three types 01 diamin'es are present in the product in the ratio:

sesame respectively, where A represents the ratio of'primary amino groups in the product to the total number of amino groups, and B represents the ratio of secondary amino groups in the product to the total number 01' amino groups. The relative proportions of primary and secondary amino groups depend upon the concentration of primary monoamine. in thereaction mixture and upon the It is ordinarily desirable'that the monoamine together with ammonia be present in the reaction mixture in concentrations of about 8 mols oi suppressor for each moi 'of dinitrile, since, 'with such concentrations oisuppressor, yields of from es per cent to 90 per cent oi theoretical are usually obtained. It more than 8 mols oi suppressor are present, the increase in yield does not ordinarily justiiy the consumption of the additional suppressor. sumption of suppressor is not considered as im-'- 'portant as higher yields, very satisfactory renlts However, obviously, when the conmay .be obtained using considerably more'than 8 .mols of suppressor. Similarly, where low yields are not considered objectionable, the process may be carried out using'ver much lower concentratime of ammonia and primary amine mixtures.

Although N-s'ubstituted diamines may he formed by hydrpgenating dinitrile's in the'absenoe of ammonia and the relative proportions of primary and secondary amino groups in the product may be varied by varying the concentration of monoamine in the initial reaction mixture. control of the reaction in this manner is not ordinarily desirable since, in the absence oi ammonia, low yieldsof diamines are obtained when the concentration of monoamine is too low. In ear- 2 rying out the process 01' the present inyention the the reaction product is controlled by diluting the monoamine withammoniawhile maintaining thetotal concentration of monoamine and ammonia at a valueoi. sumciently high to give the desired total yield ofv diamines. i

The manner'in which the degree of methyla- I Ytion of the amino groups varies with the concentrationof methylamine in the hydrogenation of dinitriles with and without ammonia as a suppressor is illustrated by the curves shown in the drawing, in which:

Fig. 1 is a curve showing the manner in which the percentage of. methylation of decamethylene diamines jvaries with varying concentration of the methylamine, in the absence of ammonia; and Fig. 2 consists of curves showing the manner in which the percentage of methylation of the product varies with the concentration of methylamine in a reaction mixture containing sebaconitrile or adiponitrile, where thetotal amount. of

, methylamine and ammonia is'maintained at a value of eight mols per mol of dinitrile.

To obtain the curve shown in Fig. 1. one. mol of sebaconitrile was hydrogenated in the presence of a :Ran'ey nickel catalyst under an initial pres-. [sure or about 1400 pounds'per square inch and at atemperatureor about 125 C. using varying amounts of methylamine. It can be seen from the curve in Fig. 1 that the percentage f,methylation rises rapidly "as the concentration of methylamine is increased; reaching a value or about 50 per cent secondary amino groups when the concentration of methylamine is about 8 mols per 1 mol of sebaconitrile. Thereafter the perv oentage methylation increases only very slightly with increase in rnethylamine concentration reaching a valueof, only about 58 per cent at a concentration oi 16 mols methylamine permol oi sebaconitrile. The degree of substitution was determined by a diiiere'nce method based on a modification of the Van Slyke method for the determiination of primary amino nitrogen in amino ac ds.

To obtain the curves shown in Fig. 2, a series of hydrogenation reactions similar to thosedee ratio of primary to secondary amino groups in j The following specific examples will illustrate the manner in which the degree or allrylation and the yield vary with the concentration of monoamine and ammonia.

Ex p e 1 A two liter hydrogenation bomb was charged with one 'mol 'of sebaconitrile (164 grams) and 100 cc. of alcoholic suspension of Raney nickel catalyst (containing about ten grams of nickel).

. The bomb was then placed in av dryice box to cool it to a temperature at which methylamine could be introduced in theiliquid state. Alter se'veralhours the bombwas removed from the box and eight mols (248 grams) of liquid math-- ylamine was introduced. The bomb was sealed I and hydrogen was admitted until the pressure in the bomb had reached 1400 pounds'per square inch. The bomb was then heated and subjected. V

to'a continuous rocking. The pressure rose slowly until-the temperature'reached about 90 C. and then commenced to fall; The pressure at 100 C.

was 1700 pounds per, square inch and after one hour at 125 C. was 1000 poundsper square inch. .The bomb was then cooled and the product was rinsed out with alcohol. The product was; then filtered free of catalyst and distilled. The distillaie boiled at 142? C. under an absolute pressure v of 12 mm. of mercury. The percentage methylation was 50.2 percent and the yield of decameth- 'ylene' diamines was 162 g'rams orj8'7 per cent based on a molecularweight of 186.1.

- Emmplel The procedure described in- Example 1 was repeated using a reaction mixture of one mol of 1 sebaconitrile (164 grams) and 15.5 mols of methylainine (480 grams). The product. was 162 grams or decamethylene diamine mixture which scribed above in connection with Fig. 1 were car ried out except that'for each mol of sebaconitrile "a total of eight mols 0f suppressor, made up oi.

methylamine and ammonia was present in the initial reaction mixture. A similar series of reactions was carried out using adiponitrile in place of sebaconitrile. The curves show the variation in percentage of secondary amino groups in the product as the mol per cent of methylamine in the eight mols of suppressor orthe original reaction mixture is varied from zero to 100 per cent.

It can be seen from the curves that the percentage of methylation increases steadily from zero to about per cent as the mol per cent of methylamine increases irom.zero to 100 per cent.

ammoniaand] methylamin'e used 'will depend upon theproperties desired in the fina PO Y- amide. j

. the desired yield. The relative proportions of had 58 per cent of itslafmino groups methylated.

The yield was 86 per cent of the theoretical yield.

Example 3 .The procedure described in Example 1 was re peated' using a reaction mixture of 1 mol of sebaconitrile (164 grams) and 3.55 mols of methylamine grams); The resulting deoamethylene diamine mixture was 36 per cent methylated. The yield Example 4 The procedure of Example 1 was repeated using a reaction mixture of 1 mol of sebaconitrile (164 grams) 4 mols of ammonia (68 grams) and 4 mols of methylamine (124 grams) The resulting V decamethylene diamine mixture was 12 percent methylated and the. yield was 86 per cent of theoretical. Example 5 The procedure ,of Example 1 was repeated using 7 2 mols of adiponitrile (216 grams) in place of sebaconitrile and 16 mols (496 grams) or methylamine. The yield of methylated hexamethylene diamines was 202 grams or '78 per cent of theoretical. absolute pressure of 14 mm. of mercury. The percentage methylation was 47.8 per cent.

Example 6 Two mols of adiponitrile (216 grains) were hydrogenated in the presence oi a Raney nickel catalyst together with'5.35 mols of ammonia (91 grams) and 10.64 mols of methylamine .(330' grams); The yield of mixed hexamethylene diwas 75.6 per cent of theoretical.

The productboiled at 92 C. under an 54 grams mol) of adiponitriie were hydrogenated over a Raney nickel catalyst in the presence of l'l'igrams (3 mols) of monopropyl amine. The product consisted of 28 grams of propylated hexamethylene diamines in which 42 per cent of the'amino groups were substituted.

In the above described examples, the initial cooling of the bomb was for the purpose or allowing liquid methylamine to be introduced without the application of pressure. Obviously, the step of cooling may be dispensed with when the liquid methylamine is forced into the bomb under pressure. Any othersuitabie hydrogenation catalyst will be found satisfactory for the reaction. The hydrogenation pressure is not critical and may be varied over an extremely wide range.

In place of methylamine, any other primary monoamine may be employed made up of an amino group Joined to the radical which is desired as the amino substituent in the final prod- ,uct. As examples of such primary monoamines may be mentioned n-propyl amine, n-butyl amine, n-amyl amine, or cyclohexyl amine; The percentage of substitution in the final product decreases with corresponding concentration of monoamine in the initial reaction mixture as the molecular weight or the amine increases.

The primary monoamines of molecular weight higher than ethylamineare liquids at ordinary temperatures'and pressures and may therefore be introduced into the hydrogenation bomb without cooling and without the application of pressure. When methylamine or ethylamine, which are gaseousatroom temperatures and pressures, are employed, it is also possible to introduce them into the hydrogenation bomb without cooling A methylene diamine, N-methyl decamethylene diamine and N, N dimethyl decamethylene diamine, said diamines being presentin the diamine mixture in such. amounts that the mol traction of diprlmary amine is A, the mol fraction of primary-secondary diamine is 2A3 and the mol fraction of disecondary diamine is B, where A is the mol traction of primary amino groups and B is .the mol fraction of secondary amino groups in the diamine mixture, which method comprises catalytically hydrogenating sebaconitrile in the liquid phase in the presence of about-8 mols of a mixture of methyl amine and ammonia per mol of sebaconitrile, both methylamine and ammonia being present in the mixture in substantial amounts.

2. The method of producing a mixture or hexamethylene diamine, N-methyl hexamethylene diamineand N, N dimethyl hexamethylene diamine, said diamines being present in the diamine mixture in such amounts that the mol fraction 01' diprimary diamine is A, the mol fraction of primary-secondary diamine is 2 ABand the mol fraction of disecondary diamine is B, where A is the mol fraction of primary amino groups and B is the mol fraction of secondary amino groups in the diamine mixture, which method comprises catalytically hydrogenating adiponitrile in the liquid phase in the presence of about 8 mols of a, mixture of methyl amine and ammonia per mol of adiponitrile, both methylamine and ammonia being present in the mixture in substan- -tial amounts.

3. The method of producing a mixture of polymethylene diamine, N-alkyl polymethylene diand without the application of pressure it they are introduced in the form of aqueous solutions,

such as a per cent aqueous solution of methylamine or a '70 per cent aqueous solution or ethylamine. The total yield is about the same as that obtained with anhydrous amines but the degree of substitution is considerably lower, being usually not more than about 40 per cent.

- The invention hasgbeen descrlbedin terms of its specific embodiments. Certain modifications and equivalents will be apparent to those skilled in the art. These modifications and equivalents are intended toibe, included within the scope of the present invention which is to be limited only amine and N,N.dialkyl polymethylenediamina said diamines being present in the diamine mixture in such, amounts that the mol fraction of v diprimaryamine is Apthe mol traction of primary-secondary diamine is 2A3 and the mol fraction or disecondary diamine is B, where A is the mol fraction of primary amino groups and by the reasonable scope of the appended claims.

What is claimed is! Bis the mol fraction of secondary amino groups in the diamine mixture, which method comprises catalytically hydrogenating a polymethylene dicyanide selected from the group consisting of I sebaconitrile and 'adiponitrile in the liquid phase in the presence or about 8 mols, per mol of nitrile, of a mixture of ammonia and a monoalkylmonoamine containing not more than 6 carbon atoms, both ammonia and monoalkyl monoamine being present in the mixture in substantial amounts.

4. The method described in claim 8 wherein the monoalkyLmonoamine is methylamine.

' BURNABD s. areas. 

